KR0146003B1 - Dielectric ceramics - Google Patents

Abstract

Disclosed is a dielectric ceramic having a high dielectric constant and a high Q (1 / dielectric loss) value in a high frequency band. The present invention provides a dielectric ceramic represented by the general formula (Ca _x Ba _y Sr _z ) TiO ₃ , where 0.8 ≦ x ≦ 0.9, 0 ≦ y ≦ 0.15 and 0.98 ≦ x + y + z ≦ 1.02. The dielectric ceramics have dielectric constant and QX f (frequency) values of 180 to 270 and 3000 to 6700, respectively. According to the dielectric ceramic of the present invention, the resonator can be miniaturized and high in quality.

Description

Dielectric ceramics

1 is a diagram showing the composition of the dielectric ceramics of the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to dielectric ceramics, and more particularly to dielectric ceramics having high dielectric constant and high Q (1 / dielectric loss) value in the high frequency band.

In general, dielectric ceramics are materials of components used in applications such as wireless mobile communications, satellite communications, microwave devices. In such applications, dielectric ceramics are used as dielectric resonators to improve filter characteristics and frequency stability. For example, when a certain frequency is determined in wireless communication, a resonator for resonating at a specific frequency is inversely proportional to the square root of the dielectric constant. Therefore, in order for the resonator to have a small size and high quality, the dielectric constant must be large, and the high Q value (1 / dielectric loss) and the temperature stability of the resonance frequency different from the temperature must be excellent.

Well-known dielectrics are xBaO-yTiO ₂ -zSm ₂ (5≤x≤23, 57≤y≤82.5, 2.5≤z≤37.5) disclosed in U.S. Patent No. 4,330,631, having a dielectric constant of 30 to 80 and a Q value of 50 to 3000 or so. The material having a higher dielectric constant is Sr _{3 (1-x)} Ca _3x Ti ₂ O ₇ (0.1 ≦ _x ≦ 0.55) disclosed in U.S. Patent No. 5,002,913, and has a dielectric constant of 80 to 150 and a Q value of 200 to 1400.

However, the above-described dielectric of US Pat. No. 4,330,631 has a low dielectric constant for miniaturizing the resonator, and the dielectric of US Pat. No. 5,002,913 is slightly larger in dielectric constant but not sufficient to miniaturize components.

Accordingly, an object of the present invention is to provide a dielectric ceramic having a high dielectric constant in the high frequency band.

In order to achieve the above object, the present invention is represented by the general formula (Ca _x Ba _y Sr _z ) TiO ₃ (wherein 0.8≤x≤0.9, 0≤y≤0.15 and 0.98≤x + y + z≤1.02) Provide dielectric ceramics.

The dielectric ceramics have dielectric constants and Q X f (frequency) values of 180 to 270 and 3000 to 6700, respectively.

According to the dielectric ceramic of the present invention, the resonator can be miniaturized and high in quality.

Hereinafter, with reference to the accompanying drawings will be described an embodiment of the present invention;

1 is a view showing the composition of the dielectric ceramics of the present invention, the manufacturing method thereof is as follows. First, CaTiO _3, SrTiO ₃ and BaTiO ₃ material by mixing each of the combining ratio in the composition for the ball mill (ball mill) mixed with water and ground in a made with the slurry (pasty), and then dried at about 80 ℃. The dried powder is maintained at 1000 ° C. for 3 hours to react with a single lobe of the closed lobesite type and then pulverized into fine powder with good sinterability. In order to improve moldability in the pulverized powder, 1 wt% of PVA (polyvinyl alcol) and water are added, and the ball mill is performed for 24 hours.

Next, the mixed slurry is further prepared into fine powder after drying and decomposition at 80 ° C. The fine powder thus prepared is put in a cylindrical mold and molded at a pressure of 900 to 1000 Kg / cm ² with a diameter of 17 mm and a height of 7 to 8 mm. The molded specimen is sintered and cooled for 3 hours in air at a temperature of 1250 ~ 1350 ℃, and the dielectric constant and QXf value are measured by dielectric resonance method at room temperature. The QXf values for each composition are shown in the table.

As shown in the above table, in the dielectric ceramics of the present invention, the dielectric constant is 180 or more and about 180 to 270, and the QXf value is 3000 or more and about 3000 to 6700. In the table, the present invention can be seen that the specimen composition is in the range of 0.8≤x≤0.9, 0≤y≤0.15 and 0.98≤x + y + z≤1.02. As described above, according to the dielectric ceramics of the present invention, the dielectric constant of 180 or more and the QXf value of 3000 or more are satisfied to achieve miniaturization and high quality of the resonator.

Claims (2)

Dielectric ceramics represented by the general formula (Ca _x Ba _y Sr _z ) TiO ₃ , where 0.8 ≦ x ≦ 0.9, 0 ≦ y ≦ 0.15 and 0.98 ≦ x + y + z ≦ 1.02. 2. The dielectric ceramic of claim 1, wherein the dielectric ceramics have dielectric constants and Q x f values of 180 to 270 and 3000 to 6700, respectively.